Opening the faucet should deliver refreshing water, not mysterious smells. Detecting something pungent, sour, or simply odd is enough to concern anyone about their water quality—that nagging worry about potential problems is difficult to dismiss. However, before alarm sets in (or you begin hoarding bottled water), understand that specific odors can actually provide helpful clues rather than immediate cause for alarm.

“Smells can tell you a lot about what’s going on in your home,” says Leonard Russo, a general contractor and owner of Elite Home Contracting. Throughout his 30-year career in home construction and remodeling, he’s encountered numerous peculiar water odors. “Sometimes it’s nothing serious, and other times, it’s a sign that something needs attention.”

Continue reading to understand how to interpret your water’s unusual odors—and recognize when professional assistance becomes necessary.

Chlorine-Scented Water

A pronounced chlorine odor (resembling laundry bleach) typically results from municipal water treatment processes. “Most cities disinfect their water systems with chlorine; it’s usually not as harmful as people think,” Russo notes. This smell may intensify during seasonal system flushing or immediately following maintenance work.

Safety concerns: Chlorine-treated water is generally safe for consumption, though allowing it to sit uncovered or running the tap briefly can help the odor fade.

When to call an expert: If the smell is exceptionally strong or won’t dissipate, contact your local water utility to verify maintenance schedules or request water quality testing.

Rotten Egg Odor

That sulfurous rotten-egg smell typically indicates sulfur gas presence, commonly originating from your hot water heater. “It’s typically the anode rod deteriorating inside the tank,” Russo clarifies. (Anode rods attract rust-causing ions from water, safeguarding your hot water tank.) As this component degrades, it reacts with water to create hydrogen sulfide gas, producing the characteristic smell.

Safety concerns: While the odor itself poses no danger, it’s unpleasant and suggests your water heater may be approaching the end of its useful life (typically seven to 13 years).

When to call an expert: If you regularly detect sulfur odors, particularly with an older water heater, contact a licensed plumber specializing in water heater maintenance. They’ll examine the tank, replace the anode rod, or suggest complete water heater replacement.

Sewage-Like Smell

Sewage odors are frequently misattributed to contaminated water, but they may actually emanate from your drainage system. “It’s common in bathrooms or basement sinks that don’t get much use,” Russo observes. When water in the P-trap (a plumbing component with a u-shaped curve that blocks odors) evaporates, it permits sewer gases to enter your living space.

Safety concerns: Though unpleasant, this typically doesn’t pose health risks. Regular water usage maintains trap water levels and prevents the odor.

When to call an expert: If running water doesn’t resolve the issue, contact a plumber to examine your traps or vents for leaks or obstructions.

Musty or Earthy Aroma

An earthy, damp odor can indicate mold, mildew, or mineral accumulation, particularly with well water or aging plumbing. “Iron and organic matter can collect in your pipes, and over time, it creates that musty scent,” Russo explains.

Safety concerns: The water is typically safe but may taste unusual or discolor fixtures.

When to call an expert: For older homes, a plumber experienced with wells and filtration systems can suggest appropriate water filters or iron-removal systems for your property. “You don’t just want a wrench turner,” Russo advises, referencing the slang for general technicians or handypeople.

Fishy Odor

A fishy smell often signifies trace minerals like barium and cadmium in your water supply. These are generally harmless but can influence taste.

Safety concerns: The water remains safe for most purposes, though some prefer filtering it for reassurance.

When to call an expert: If the odor bothers you, have a plumber or water treatment specialist analyze your water and install filtration if warranted.

Metallic Smell

A penny-like smell or taste suggests corroded or deteriorating pipes—typical in older properties with lead or cast-iron plumbing. “As those pipes deteriorate, small amounts of metal can leach into the water,” Russo states.

Safety concerns: Lead exposure, even minimally, poses serious risks, especially for households with children. Avoid drinking or cooking with the water until testing occurs.

When to call an expert: Contact a licensed plumber immediately. They can evaluate your system and explore repiping options using safer materials like copper or CPVC.

Gasoline or Natural Gas Smell

A subtle gasoline or natural gas odor demands immediate action. “Any time gas comes up, I get concerned about safety,” Russo emphasizes. “If you think you smell gas in your water, stop using it right away.”

Safety concerns: Exposure can cause headaches, dizziness, and lightheadedness. Avoid running taps, lighting flames, or using electrical appliances until confirming the source is safe.

When to call an expert: Contact your gas utility immediately. They can test for leaks or contamination and verify your home’s safety.

Maintaining Fresh Water Throughout the Year

Even pristine water can develop odors without consistent maintenance. Russo advises having a reliable plumber inspect your system annually and periodically flush your water heater. “Nine times out of 10, when something’s off with your water, your plumber’s your best friend,” he notes.

Whole-house filtration or water-softening systems can also prevent odors, protect plumbing, and improve water taste. For older homes, don’t dismiss subtle changes; your sense of smell often detects issues before your plumbing shows obvious problems. As Russo explains, “When you have someone who knows your home inside and out, that relationship is priceless. Because when your water starts to smell funny, you’ll want to call someone who’ll pick up.”